Experimental Analysis On Settlement Characteristic Of Railway Ballasted Track Bed Under Cyclic Loading

With the rapid development of railway technology towards high-speed and heavy-load, the traditional railway ballasted track bed sustains more and more force from the train, which accelerates deformation of track bed. While the deformation of track bed is mainly reflected in the settlement, which is constantly formed by accumulation pattern under cyclic loading, meanwhile, it will influence the train running safety, comfort and increase maintenance costs of track bed. To this problem, this thesis analyzed the settlement characteristic from the perspective of experiment, so as to provide reference for the ballasted track bed disease prevention and maintenance.This thesis comes from the yunnan province education department scientific research fund project "Research on Modeling Simulation Technology of Railway Ballasted Track Bed Based on Discrete Element"(No2012Y541).Through a large quantity of literature investigation, this thesis comprehensively reviewed the domestic and foreign research situation of track bed settlement, summarized the main calculation models of track bed settlement at domestic and foreign, and analyzed their characteristics, all of these provided a better theory foundation for this thesis. Meanwhile, based on the domestic and foreign research achievements,1:1 track bed cyclic loading test system was established, which was consisted of three parts, rail system, loading system and data testing and acquisition system. The system can be used to simulate how different factors affect the response and settlement characteristics of track bed, such as the axle load of the train vehicle, vehicle velocity of the train, the track condition and so on, and based on the experiment system, the experiment scheme of this thesis was proposed.Based on cyclic loading test system, response test and cyclic loading test of track bed under different vehicle velocity of the train were carried out. According to the results of response test, analyzed how the vehicle velocity of the train affect the response of track bed, test analysis results show that the vibration acceleration of ballast and the dynamic pressure of track bed increase with the improvement of vehicle velocity. Based on the cyclic loading test results, the settlement characteristic of track bed under cyclic loading was analyzed under the vehicle velocity of 80 km/h、100 km/h、120 km/h、140 km/h、160 km/h. Three regression curve models were use to regression analyze the settlement experimental results of ballasted track bed under different velocity, and compared these regression models, the optimal regression model in accordance with test results is confirmed. Based on railway maintenance engineering practice, it can preliminary provide to predict the settlement of track bed under different vehicle velocity, so as to provide certain reference for the railway maintenance departments. And furthermore, the reliability theory is put forward to apply to study the settlement of ballasted track bed.Based on the test results, it was analyzed the vehicle velocity on the influence degree of track bed settlement from two aspects of average accumulation settlement and settlement increment in the process of loading, and the thesis preliminary illustrated the relationship between response parameters and settlement of track bed, which laid a foundation for further study.